<div
  class="ui-grid-tree-base-row-header-buttons"
  ng-class="{'ui-grid-icon-minus-squared': grid.treeBase.numberLevels > 0 && grid.treeBase.expandAll, 'ui-grid-icon-plus-squared': grid.treeBase.numberLevels > 0 && !grid.treeBase.expandAll}"
  ng-click="headerButtonClick($event)">
</div>
